[393] Described next
are three Navy attack aircraft (one is also used by the USAF) that
appeared between 1954 and 1964. The three aircraft relied heavily
on fighter technology of the 1950's, but in contrast with fighters
of that period, none had a supersonic capability. Hence, none
incorporated area ruling and none was equipped with afterburning
engines. All three aircraft were equipped with power-operated
controls and arresting hooks for carrier operation; all had
pressurized cockpits and ejection seats for crew escape. Designed
under the restraints imposed by aircraft-carrier operation, the
three differed primarily in their range-payload characteristics
and the conditions under which they were expected to operate. Yet,
just as with the fighters of the mid-1940's, they differed
markedly in appearance.

Douglas A-4 Skyhawk

Designed as a light naval attack aircraft
capable of delivering a nuclear weapon, the Douglas A-4 Skyhawk
(A4D in the old Navy nomenclature) made its initial flight on June
22, 1954. When the last aircraft of this type rolled off the
production line in February 1979, a total of 2096 units had been
produced in a remarkably long 25-year production history. These
ubiquitous aircraft have been in the military inventories of nine
different countries, one being the United States, and have seen
action in numerous world trouble spots including Vietnam, the
Middle East, and the Falkland Islands where they served with the
Argentine forces. Although retired from United States Navy fleet
use in 1976, the aircraft is still used extensively by various
elements of the Navy and Marine Corps for training and utility
purposes. The A-4 is also currently [394] flown by the
famous Navy Blue Angels exhibition team. Approximately 15 variants
of the A-4 were produced during its long production life. Although
primarily a single-place aircraft, the Skyhawk has also been
produced in a two-place trainer version known as the TA-4.

Shown in figures 12.22 and 12.23 are two
versions of the Skyhawk, and data for the A-4E are given in
table
VI. Configuration of the aircraft
is characterized by a cropped delta wing of 33° sweepback
mounted in the low position on a short, stubby fuselage with a
large vertical tail and dorsal surface. The horizontal tail is
mounted part way up the vertical fin just above the wing chord
plane extended and consists of an electrically actuated stabilizer
and hydraulically powered elevator. The hydraulically actuated
rudder is of a unique design, consisting of a single central skin
with external riblike stiffeners. (See figs. 12.22 and 12.23.)
According to the interesting account of the development of the A-4
given in reference 164, this design feature was found to offer a solution
to problems of rudder buffet or buzz.

Two inlets mounted high on the fuselage
just ahead of the wing supply air to the single Pratt &
Whitney turbojet engine of 8500....

....pounds thrust. Clearly shown in figure
12.23 are the boundary-layer diverters located Just ahead of the
inlets. The long landing-gear struts were dictated by clearance
requirements for large stores carried beneath the wings on either
side and between the main landing-gear legs. A braking chute was
provided for use at shore-based landing facilities.

For simplicity, the wing of aspect ratio
2.91 was built as a single unit with continuous top and bottom
skins. it was so small that no folding was necessary for storage
and movement on the aircraft carrier, an unusual feature in a Navy
aircraft. Automatic leading-edge slats and trailing-edge split
flaps were provided for lift augmentation. Outwardly extending
speed brakes were mounted on either side of the rear of the
fuselage.

The Skyhawk is capable of carrying
literally hundreds of combinations of external stores including
fuel tanks, both conventional and nuclear bombs, rockets, and
Sidewinder missiles. Armament consists of two 20-mm cannons, one
of which is mounted in each wing root.

The data in table VI show that the Skyhawk has a remarkably low gross
weight of 18 311 pounds but can deliver a weapons load of 2040
[396]
pounds at a mission radius of 680 miles with two 300-gallon
external tanks; unrefueled ferry range is 2130 miles. Maximum
speed of the aircraft is 673 miles per hour (Mach 0.88) at sea
level, and cruising speed is 498 miles per hour. Ceiling is just
over 40 000 feet. Certainly, the aircraft has an impressive
performance for a lightweight attack aircraft.

The Skyhawk was designed at a time when
the complexity, weight, and cost of combat aircraft were
escalating at an alarming rate. Under the supervision of designer
Edward H. Heinemann, an intensive effort was made during the
design and development of the aircraft to keep it light and
uncomplicated (ref. 164). The effort paid off so well that the first
version of the Skyhawk had a gross weight of only about 15 000
pounds. Growth in capability resulted in the increase in gross
weight to 18 311 pounds shown in table VI for the A-4E. The light weight of the aircraft
caused it to have at least two appellations: "The Bantam Bomber"
and "Heinemann's Hotrod." The long production life of the Skyhawk,
together with its widespread use in a variety of roles, attests to
the basic soundness of the original design and its potential for
growth and adaption to differing requirements. The Skyhawk should
continue to be a familiar sight for many years.

Grumman A-6 Intruder

The Grumman A-6 Intruder was designed in
response to a Navy requirement for a true all-weather attack
aircraft capable of precision weapons delivery at night under
conditions of zero visibility. These difficult mission
specifications dictated a relatively heavy, twin-engine aircraft
manned by a crew of two, consisting of a pilot and a
weapons-systems operator, and equipped with a complex array of
electronic gear.

First flight of the A-6 (A2F-1 in the old
Navy designation system) took place in April 1960, and the first
squadron to use the aircraft was formed in early 1963. Operational
sorties against North Vietnam were begun in 1965 from carriers
located off the coast. The A-6 and its derivatives have been in
continuous production since 1960 and are still rolling off the
production line at this time. A close relative of the A-6 is the
EA-6B Prowler electronic warfare aircraft, which first flew in May
1968. The Prowler differs from the Intruder mainly in the amount
and type of equipment carried and in the use of a four-man instead
of a two-man crew.

The A-6A is shown in figures 12.24 and
12.25, and physical and performance data are given in table VI for the more advanced A-6E.

Configuration of the midwing subsonic
aircraft features a 5.31-aspectratio wing of moderate sweepback
(25°) and one turbojet engine nestled on either side of the
fuselage in the intersection of the lower wing surface and the
fuselage side. Exhaust nozzles are located just behind the wing
trailing edge, and, as can be seen in the figures, side-mounted
inlets are low and far forward on the fuselage. A side-by-side
seating arrangement accommodates the crew in the A-6. Clearly seen
in the photographs is the refueling probe located on top of the
fuselage just ahead of the cockpit canopy. To provide the lift
augmentation necessary for carrier operations, nearly full-span
leading-edge and trailing-edge high-lift devices are installed.
The deployed leading-edge slat can be clearly seen in figure
12.24. The trailing edge of each wingtip outboard of the fold line
splits to form speed brakes that deflect above and below the wing
when deployed. As seen in figure 12.25, the outer portion of the
wing folds upward to facilitate carrier storage. Also evident in
the figure is one of the two short flow-control fences located on
each wing. Spoilers are used for lateral control, and the
longitudinal control surface is an all-moving horizontal
tail.

No guns of any kind are carried aboard the
A-6, and the aircraft has no internal bomb bay. A wide variety of
stores, however, can be....

....mounted externally; these include both
conventional and nuclear bombs, fuel tanks, and an assortment of
rockets and missiles. Two of the store-mounting stations are
visible in figure 12.25.

As shown in table VI, the A-6E is capable of a maximum speed of 653
miles per hour (Mach 0.86) at sea level and a cruising speed of
390 miles per hour. Although the wing loading of the A-6E is over
40 percent higher than that of the A-4E, the stalling speeds of
the two aircraft are nearly the same, which attests to the
effectiveness of the highlift devices on the A-6. The zero-lift
drag coefficient of the A-6E is about 20 percent higher than that
of the B-57B; however, the maximum lift-drag ratios of the two
aircraft are about the same. The higher-aspect-ratio wing of the
A-6E compensates for its higher zero-lift drag coefficient in
determining the maximum lift-drag ratio.

As with all versatile attack aircraft,
many combinations of payload and mission radius are available to
the A-6E. For example, a weapons load of 2080 Pounds consisting of
a Mark 43 nuclear bomb can be delivered at a mission radius of'
890 miles. For that mission, four 300-gallon external tanks are
carried. Alternatively, 10 296 pounds can be delivered at a
mission radius of 450 miles with two 300-gallon external
[399]
tanks. Unrefueled ferry range is 3300 miles. Normal gross weight
aircraft is 54 393 pounds, nearly three times that of the
A-4E.

The subsonic A-6 has no spectacular
performance or design features but is superbly suited to the
particular attack role for which it so carefully tailored. The A-6
Intruder and its close relative the EA-6 Prowler will no doubt
continue in service with the U.S. Navy and Marine Corps for the
foreseeable future.

Vought A-7 Corsair II

As applied to an aircraft, the name
Corsair has its origins in a series of famous biplanes built for
the Navy by the Vought Corporation between World Wars I and II.
Later, the name was applied to the famous Vought F4U series of
fighters flown by Navy and Marine pilots during World War II.
Discussed next is the modern-day descendant of these historic
aircraft - the Vought A-7 Corsair II.

The Corsair II was developed in response
to a Navy requirement for a single-place, fair-weather subsonic
attack aircraft capable of carrying a much heavier weapons load
than the Douglas A-4 Skyhawk. First flight of the new aircraft
(Vought A-7D) took place on September 27, 1965, and it has been in
continuous production since then with a total of 1534 units
produced by mid-1980. In addition to the Navy and Marine Corps,
the USAF as well as air forces of two other nations operate the
A-7. The definitive versions of the aircraft are the USAF A-7D and
the closely related Navy A-7E. An in-flight view of an A-7D is
shown in figure 12.26, and a close-up view of an A-7E is pictured
in figure 12.27. Physical and performance data are given in
table
VI for the A-7D.

That the lineage of the A-7 can be traced
directly to the Vought F-8 Crusader fighter is obvious from a
comparison of figures 12.26 and 12.27 with figures 11.19 and
11.20. Like the F-8, the configuration of the A-7 is characterized
by a high wing, low horizontal tail, chin inlet, and short
landing-gear legs that retract into the fuselage. Since the A-7 is
a subsonic aircraft, however, no area ruling is incorporated in
the fuselage, which is also shorter and deeper than that of the
supersonic F-8. Because of the larger mass flow of the turbofan
engine employed in the A-7, the size of the chin inlet is somewhat
larger than that of the turbojet-powered F-8. These differences
make the A-7 appear shorter and more stubby than the earlier
fighter. The A-7...

The wing of the A-7 is closely related in
geometry and physical size to that of the F-8. (Compare data in
tables V and VI.) Leading flaps and single-slotted trailing-edge
flaps are fitted to the wing, as are upper surface spoilers
located ahead of the flaps. Not used on the A-7 is the unique
variable-incidence feature of the F-8 wing. The shorter length of
the fuselage together with the slight "upsweep" of the underside
of the afterbody (fig. 12.27) allow the A-7 to be rotated to a
significantly higher pitch angle on takeoff and landing, without
tail scrape, than was possible for the F-8. The higher available
ground pitch attitude, together with the good augmentation
capability of the high-lift system, no doubt played a large part
in obviating the need for a variable-incidence capability in the
wing. Speed brakes are located on the bottom of the fuselage about
midway between the nose and the tail. A braking chute is provided
for use in shore-based operations.

Original power plant of the A-7 was a
nonafterburning version of the Pratt & Whitney TF30 turbofan.
This is the same engine that, equipped with an afterburner, powers
both theF-111 and the F-14.Beginning with the A-71), however,
the more powerful Allison TF41-A-1 turbofan was installed. An
American-made version of the British Rolls-Royce Spey, the
TF41-A-1 has a bypass ratio of 0.7 and uses a five-stage
fan.

A wide assortment of external stores can
be accommodated on the A-7. Eight store-mounting positions are
provided. There are three pylons under each wing, and a single
mounting station is located on each side of the fuselage. Two of
the underwing pylons and one of the fuselage mounting stations are
visible in figure 12.27. A total of 15 000 pounds of stores can be
carried. Table
VI shows that 6560 pounds can be
carried on a typical mission with a radius of 556 miles. A
six-barrel 20-mm Vulcan cannon is located on the left side of the
fuselage near the bottom of the aircraft. A portion of the muzzle
of the gun is visible below the word "intake" in figure
12.27.

Although the A-7 was originally intended
as a fair-weather aircraft, later versions (beginning with the
A-7D) were equipped with extensive electronic gear for all-weather
operations. The various modes in which this equipment may be
utilized in attack operations, along with many other aspects of
the A-7 story, are discussed in reference 136.

According to the data in table VI, the gross weight of the A-7D is a little more than
twice that of the A-4E but is significantly less than that of the
A-6E. Maximum speed of the A-7D is listed as 663 miles
[402]
per hour (Mach 0.89) at an altitude of 7000 feet. Stalling speed
at maximum gross weight is a very high 174 miles per hour. For
landing on an aircraft carrier following a mission, however, a
weight much less than the maximum value, along with a reduction in
stalling speed, would normally be expected. For example, with a
weight of 23 000 pounds, the stalling speed would be about 135
miles per hour.

The A-7 is one of those aircraft with a
demonstrated capability of performing well in a wide variety of
missions. Other aircraft are faster or have a greater
range-payload capability or have a faster rate of climb;
sometimes, certain of these characteristics is deemed so important
that it dominates the entire design. What results is a "point
design" aircraft that can perform one mission extremely well but
is relatively much less effective in any other mission. The design
parameters of the A-7 were chosen so that the aircraft has great
mission versatility. It was successfully employed in just about
every conceivable attack role during the Vietnam conflict where it
first saw action in 1967.